1. Field of the Invention
This invention relates to an interchangeable lens type camera system which is provided with both an optical zoom means and an electronic zoom means.
2. Description of Related Art
The advancement of image pickup apparatuses such as video cameras, etc., has been conspicuous during recent years. The functions of these apparatuses are thus being diversified and their operability is being improved.
As a result of the functional diversification, there have been made many improvements on the video cameras, for example, an interchangeable lens type camera system has been introduced into the field of the video cameras, thereby making them usable for all shooting conditions. Further, an electronic zoom means for electronically magnifying an image also has been introduced into the video cameras, so that an image which has been magnified by an optical zoom means is further magnified by an electronic process. Therefore, such high magnifying rates that are not attainable with an optical zoom lens alone have become attainable.
Meanwhile, video cameras provided with both an optical zoom means and an electronic zoom means and arranged to perform a zooming action by a combination of the two zoom means have been disclosed in U.S. Pat. No. 4,843,475, U.S. patent application Ser. No. 08/078,565 filed Jun. 17, 1993, etc. Each of these video cameras has a lens unit undetachably fixed to a camera body and is thus arranged to permit control to be always univocally performed on the optical zoom means and the electronic zoom means. However, these video cameras are, unlike the interchangeable lens type camera system, arranged without taking into consideration the necessity of matching control over the lens unit with control over the camera body.
More specifically, in the case of an interchangeable lens type camera system, since a lens unit is detachably mounted on a camera body, where a zoom lens (optical zoom means) is disposed on the side of the lens unit and an electronic zoom means is disposed on the side of the camera body, a zoom operation part may be variously arranged such that it is provided on the side of the camera body or on the side of the lens unit or both on the side of the camera body and the side of the lens unit. Therefore, it has been hardly possible to always appositely carry out control between the lens unit and the camera body.
For example, it is difficult to set timing for switching between an optical zooming process performed in the interchangeable lens unit and an image magnifying process (electronic zooming process) performed in the camera body. Further, in a case where the interchangeable lens unit has a zoom ring for mechanically moving the position of a variator lens and a slip mechanism is provided at a gear for transmitting the motion of the zoom ring, for example, there has been provided no means for cancelling the image magnifying process (electronic zooming process) on the side of the camera body when the operator operates the zoom ring toward a wide-angle side.
Further, although a good picture quality can be kept during the optical zooming process, the largest possible rate of magnification by means of a lens is naturally limited with respect to the performance of the lens, the size and weight of the system, etc. The electronic zoom means is able to make up for the insufficiency of the magnification possible by the optical zoom means. However, the electronic zooming process causes some deterioration in picture quality. Therefore, it has been extremely difficult for the interchangeable lens type camera system to optimize control over both the optical zoom means and the electronic zoom means in such a way as to obtain images in their best quality. The solution of this problem has been strongly desired.
This invention is directed to the solution of the above-stated problem. It is, therefore, a first object of this invention to provide an image pickup apparatus which is arranged to permit smooth switching between an optical zooming process and an electronic zooming process.
It is a second object of this invention to provide an interchangeable lens type camera system arranged to permit smooth switching between an optical zooming process and an electronic zooming process and to provide an adequate control over each of the two zooming processes.
To attain these objects, in accordance with a preferred embodiment of this invention, there is provided an interchangeable lens type camera system which is composed of a camera body and a lens unit detachably mounted on the camera body, comprising optical magnification varying means disposed within the lens unit, electronic magnification varying means disposed within the camera body and arranged to electronically magnify an image, lens-side control means disposed on the side of the lens unit and arranged to transmit to the camera body information used for controlling inhibition or permission of an action of the electronic magnification varying means on the basis of an operating state of the optical magnification varying means, and camera-side control means disposed on the side of the camera body and arranged to control the electronic magnification varying means on the basis of the information received from the lens-side control means.
To attain the above-stated objects, in accordance with the preferred embodiment of this invention, there is provided a lens unit adapted to be detachably mounted on a camera body having electronic magnification varying means for electronically magnifying an image, comprising optical magnification varying means, and control means arranged to transmit to the camera body information used for controlling inhibition or permission of an action of the electronic magnification varying means according to an operating state of the optical magnification varying means.
To attain the above-stated objects, in accordance with the preferred embodiment of this invention, there is provided an interchangeable lens type camera adapted to detachably mount a lens unit thereon, comprising means for receiving, from the lens unit, information about an operating state of optical magnification varying means disposed within the lens unit, image pickup means for photo-electrically converting an optical image formed through the lens unit into a picked-up image signal and for outputting the picked-up image signal, electronic magnification varying means for electronically magnifying the picked-up image signal, and control means for controlling inhibition or permission of an action of the electronic magnification varying means on the basis of the information about the operating state of the optical magnification varying means.
The above and other objects and features of this invention will become apparent from the following detailed description of embodiments thereof taken in connection with the accompanying drawings.